Liquid fuse



2 Sheets-Sheet l #La 5 mi fm 5 i o W O neu O U F 7 #s 1 F/ w% /f w WM OR. H. EARLE LQUID FUSE Filed May 5, 1932 R. H. EARLE 2,L,657

LQUD FUSE Filed May 5, 1952 2 Sheets-Sheet 2 Patented Aug. 6, 1935PATENT OFFICE LIQUID FUSE p Ralph H. Earle, Wauwatosa, Wis., assignor toLine Material Company,

South Milwaukee,

Wis., a corporation of Delaware Application May 5, 1.932, Serial No.609,452

5 Claims.

This invention relates to liquid fuses.

Objects of this inventionare to provide a novel form of liquid fusewhich will respond to overloads whether suddenly or gradually applied,

'-1 which will quickly separate the two portions of the fuse link whenfusing occurs, and'which will quickly withdraw one of the portions ofthe fuse link below the surface of an arc extinguishing liquid.

Further objects are to provide a fuse of this general type which is soconstructed that the fuse link, although capablev of being formed torespond to a small value of current, nevertheless is not subjected toundue or excessive mechanical lstrain, but which is so made that thefuse link and the method of anchoring the ends thereof providemechanical strength to withstand the initial handling, while the deviceis being re- A fused, and also to withstand the steady pull of a yspringwithout danger of any of the parts failing from mechanical weakness.

Further objects are to provide a fuse in which the fuse link is ofcomposite construction with the upper and lower parts soldered togetherbut Vwhich is ofgreat tensile strength, even at the soldered joint dueto an overlapping face to face contact of flat, ribbon like members,preferably with the ribbon member of one part received between orintermeshing with two ribbon 4members of the other part.

When fuses having soldered portions are under mechanical strain, it hasbeen found that with the usual type of soldered joint that such ljointis frequently twisted, bent or otherwise placed in such a position it issubjected to tensile strain as well as pure shear. Under theseconditions tests have shown that the action of the fuse is not whollysatisfactory. There seems to be somewhat of a gradual mechanical failingof the joint hastened whenever the joint is hot.

Further objects of this invention are to provide a novel form of fuse inwhich the soldered joint is in pure shear and cannot turn or be sopositioned that it is subjected to tensile stresses,

' which would interfere with the accurate functioning of the fuse.Instead, the joint is so made that although a considerable mechanicalstress or pull may be imparted to the joint, that nevertheless thesoldered joint is itself in pure shear and consequently a gradualfailing or an alteration of the accuracy of the fuse is avoided.

Further objects are to provide novel forms of attaching means for boththe upper and lower ends of the fuse link to not only give an adequateandfiirm mechanical attachment for the ends of the fuse link, but alsoto secure an unusually good electrical contact between the ends of thefuse and the adjacent conducting portions to which the fuse link isattached.

It has been found that with the usual types of fuses that accuratecalibration is extremely difficult and that calibration is usually veryuncertain, only a very rough approximation being secured.

This invention is designed to overcome the defects noted immediatelyabove, and further objects of this invention are to provide a novel formof fuse in which accurate calibration may be obtained with the utmostfacility, and in which the fuses, although made by quantity production,

are nevertheless substantially uniform, and in which fuse strips ofdifferent values, that is to say different fusing current values, may bemost easily constructed in a simple and relatively precise manner.

In greater detail, further objects of this invention are to provide anovel form of fuse which is so made that the 12R, watts developed issubstantially constant at the soldered joint, irrespective of thecurrent value for which the fuse is designed, the variation in currentvalue for different sizes or capacity fuses being obtained by varyingthe composition of the fuse strips or members, or by varying theircrosssectional area, preferably by varying their thickness. Thisinvention, therefore, provides a means whereby solder or other readilyfusible material having av substantially definite fusing point may beused for all sizes or capacity of fuses, and in which the same dies maybe employed, if desired, for stamping out the fuse strips or members ofthe same width, the variation in capacity of the fuse being obtained byvarying the thickness. Thus, this invention materially reduces the costof manufacture of fuses and at the same time reduces the equipmentnecessary for making fuses of different capacities. Either one or bothof the two Ways of securing different value or different capacity fusesmay be employed, or, if desired, solders of different fusing points maybe employed, although it has been found that this last method is a greatdeal more unsatisfactory and less precise than to use solder of adefinite melting point for all sizes of fuses and obtain the variationin rating or capacity of the fuse by either of the two methods detailedhereinabove.

Embodiments of the invention are shown in the accompanying drawings, inwhich:-

Figure 1 is a side elevation, partly in section, ofV the liquid fuse.

Figure 2 is a View of the upper portion of the liquid fuse, the sectionfor such view being at right angles to that of Figure l.

Figure 3 is a sectional .view on the line 3 3 of Figure 1.

Figure 4 is a sectional View on theline 4 4 of Figure 1. v

Figure 5 is an enlarged sectional view on the line 5 5 of Figure l.

Figure 6 is a further form of fuse link.

Figure 7 shows a further form of fuse link and a diiierent means ofattaching such link to the bridge member. l f

Figure 8 shows a further form of fuse linkand a diiierent way ofattaching it to the vbridge member.

Figure 9 sho-ws a further form of fuse link and a different manner ofattaching it to the bridge member.

Figure 10 shows a further form of fuse link.

Figure v11 shows a form of fuse link and mannerV Figure 16 is asectional viewon theline IS-li of Figure 8. i v Y Figure 17 is asectional View on theline irl- IT of Figure 12. i Y. f Referring to thedrawings, Vit will be :seen Eth'at the liquid fuse eomprisesa tubular orcylindrical container l, preierablyofglass or othergsuitable Yinsulatingmaterial, which is provided with a lower metal cap or contact member 2and anV upper metal sleeve or contact member'S each secured to the glasstubular body portion I in a gas and liquid tight manner.

The upper contact membengor ksleeve 3, is externally threaded andreceives' the ring nut 4. which Vtightly clampsa gasket disk, orclosure' member 5, in place., The disk 5f is formed ofa yielding andsomewhat eXpansible material such as lead, aluminum, tinfoil',l orV someother alloy which is'soft and expansible. Y

This gasket: disk 5, when clamped in place byV the ring nut e, formsagas seal, andffis adapted to be rupturedand the part closing theropening throughthe member-3 bodily blown away' when the fuse blows. Thisprovides an instantaneous relief for the pressure gases' and avoidsplacing excessivestrain upon the glass body portion.

The sleeve 3. isprovided withrdiametrically opposed slots V6 which; areopen at their upper ends and which are .provided with rounded shouldersat their lower ends. Y K strong arch like member or bridgemember 'l has.its ends rounded and seated loosely within the slots t and resting,rupon the rounded'shoulders at.

the bottom of such slots.V k This arch like member 'l is in reality astro-ng 'metal strip which is a support for the' composite fuse link.

VThe composite fuse link is preferably formedv .of an upper and a lowerportion, the upper portion consisting of tworibbn like members 8 betweenWhich'a Vsingle ribbon like` member S form` ing the lower portion issecured. The upper ribbon like members'of the fuselink pass throughv acentral aperture Lf'ormed'in the support. 1', pass' vare'preferablyformedvo ribbon, providing a suitable resistance to heat the solderedjoint.

' the melting temperature.

1 havingy a substantiallyv definite melting point may k be employed, andthat the heat developed at Y the soldered joint may be constant for allsizes of A transverse, relatively Y over the upper face of the support,and have their ends wrapped or positioned beneath the rounded ends ofthe member l. When pressure is applied to the fuse link, it is apparentthat the supporting member 'l acts likea toggle and causes a 5 i betweenthe members 8 and is soldered to such members. This forms anintermeshing or overlapping of the iat ribbon like fuse strips, whichThe material of which the ribbons or other shaped members forming thefuse link, either in 'lected for its particular characteristics. For eX-ample, different materials for dilerent amperage v linksare employed. Ahigh resistance material j like a nickel chromium alloy is employed forlow amperage "links,- and a very low lresistance material, such ascopper, may be employed for high ampera'g'e links, adjusting thematerial and the thickness of the material sol as to give a veryconstant 12R development at the soldered joint. This 12R is that whichis required to raise the solder to It is, therefore, apparent that agiven solder fuses, the capaci-ty or rating of the fuse being variedpreferably by varying the thickness of the fuse strips or members andtheir composition. This enables the manufacturer to usesubstantiall-ythe same dies or apparatus for forming the members of thefuse link, although fuse links of widely Vdifferent ratings may beselectively produced'asV desired by means of the characteristics of``this invention which have been outlined immediately above. Y

The intermediate portion of the composite fuse link. is reduced incross-section by narrowing the ribbon like members, as, indicatedgenerally at lll .in YFigure 2, so that the cross-sectional area remainsapproximately the same throughout the entire length of the fuse link. Ifdesired, the in- Y termediate portion of thefuse link may be covered bya cork or other member ii.

The lower member Q of the fuse link continues vdownwardly and issupplemented by an additional. member 9' riveted or otherwise securedthereto to provide a double thickness, Vor two ribbon like memberslfor-the lowest part ofthe lower portion of the composite. fuse link.These ribbonV like portions are separated and are positionedbeneathinturned channel shapedy arms of a lower fitting l2. Y The arms l 2 arepreferably integralwith each other and are approximately of U.-shapedformation having a iiat bottom connecting yoke I3, see Figure l.. Thechannel portions of lthese arms are indicated more clearly in Figure 5.The upper ends of the arms I2 converge or approach each other, as shownmost clearly in Figure 1.

An inverted V-shaped wedging member M, see

^ Figure' l; is positioned between'therportions 9 and 9 of the fusestrip and the arms i2 of the lower fitting,V so that whenthe loweriitting or con-V 75.Vv

r-is secured to a transverse plate I5.

suitable manner.

ducting portion is drawn downwardly, the fuse link is tightly wedgedagainst the arms I 2, see Figure 5, thereby securing an excellentelectrical contact.

It is to be noted at this point that the electrical connection betweenthe upper and lower ends of the fuse link and the adjacent conductingportions is secured, in this form of the invention, without the use ofscrews or other fasteners of this type. This construction also affords aWedging or binding contact between the fuse ends and the conductingportions, thereby securing good contact and reducing the heating atthese points. y

As shown in Figure l, it is preferable to bend the ends of the members 9and 9 over the bottom ends of the member I4 to facilitate positioning ofthe parts.

The conducting member or fitting just described Preferably the yoke I3is locked lto the plate or bar I5 by upwardly and inwardly turned earskI6 formed integrally with the bar I5, kas shown in Figures l and 4. Thebar I5 is soldered or otherwise secured to a exible leader or strandedconductor I'I whose lower end is secured to the lower terminal orcontact member 2.

A helical spring I8 loosely surrounds the leader I'I and is secured tothe lower contact 2 in any The bar I5 extends between convolutions ofthis spring and thus provides a very secure attachment of the spring tothe lower member I2.

It is preferable to provide some form of protection for mechanicallyprotecting the diaphragm 5, see Figures l and 2.` This protecting meansmay take the form of a cap I9 provided with spring fingers 20 which snapbeneath the bottom edge of the ring nut 4.

The tubular body portion is preferably completely filled with some arcextinguishing liquid, such as carbon tetrachloride. Obviously thetubular body portion may be lled to any desired height, although thecomplete filling is probably the simplest.

When the fuse blows, the diaphragm 5 is ruptured around its margins andblown, together` with the cap I9, from the fuse body. The arch shapedsupporting member is released from the `pressure and consequentlywedging of its ends and the adjacent portion of the iuse against theannular member 3 is instantly relieved, and this arch shaped member andthe remaining upper portion ol the fuse is blown bodily from the tuibular body portion.

rounded members may have reduced portions 23v and 24 cut to halfthickness and soldered together, particularly as shown in Figure l5. The'upper member 23 may be secured to the bridge member 25 in any suitablemanner. In the form shown in Figure 7 it is attached by means of a bolt26 in one of the arms of the bridge member.

Figure 8 shows a further form of fuse link in which a pair of upperwires or other shaped members 21 receive between them a lower wire orother shaped member 28 which is soldered to the upper wires at theiroverlapping portions, particularly as shown in Figure 16. Obviouslyother shapes may be employed ii desired. The upper` ends oi the members2 are secured by bolts or screws 29 to the arms of the bridge member 30.

Figure 9 shows a form of fuse link in which a pair of spaced ribbon likeor other shaped upper members 3| are secured to the underside of thebridge member 32 by bolts or screws 33. A U- shaped lower member 34 hasits arms soldered flatly 'to the members 3I and is preferably providedwith a, reinforcing metal piece 35 in its horizontal loop to which thetension spring may be attached, and to prevent folding or drawing of thearms of the member 34 towards each other.

Figure l0 shows a further form in which the upper strip 36 oi ribbon orother shaped member is not joined directly to the lower member 3l butindirectly by means of symmetrically placed, overlapping intermediateportions 38, to which both upper and lower members are soldered. Theupper end of the member 35 may be attached to the bridge piece 39 in anysuitable way, as by means of the bolt 4).

Figure 1l shows a further form of construction in which ribbon likeupper members 4I receive between them a lower ribbon like member 42which is soldered thereto, as previously described.

This construction is similar to that shown in Figure 6 except that theupper ends of each of the members 4I are separately attached to thebridge piece 43 by means of screws or bolts 44, or other fasteningmeans.

Figure l2 shows a further Yform of the invention in which the uppermember of the fuse link consists of a tubular member 45 which receiveswithin its lower end a round or wire like lower member 4S, such membersbeing soldered together, as previously described. Preferably the upperportion of the tubular member 45 is riattened and split to providetongues which may be oppositely folded, as v indicated at 4'I. Thesetongues are `secured to the bridge member 48 in any suitable manner, asby means of the bolts 49.

In the form shown in Figure 13 a different type of bridge member isemployed. This bridge member, scribed bridge members, secures the sametoggle effect as the other` members. -Howeven it consists of twohingedly joined arms 50 which may be joined by means of a pintle pin orother member 5I, as shown in Figures 13 and 14. The fuse link may-be ofany desired type.

In the form shown, two wire or ribbon meinbers 52 constitute the upperportion of the fuse link and receive between them a lower member 53. Theupper members 52 are looped over the pintle pin 5I, as shown mostclearly in Figure 14, and are secured to the arms 5U by means of thescrews or bolts 54.

It is to be noted that in this form of construction the upper contactmember 3 of the body portion of the fuse is provided with slots whichterminate in abrupt shoulders 55, as shown in Figure 13. Thisconstruction provides a sharp corner within the slot and the ends of themembers 58 .are bevelled at a sharper angle than that between theshoulders 55 and the vertical portions 56 of the slots, and consequentlysuch sharply pointed or bevelled ends of the members 50 have a linebearing. with the corner portions formed by the faces 55 and 56 of theslots. (Figacting like the other previously der ure 13 is aVfragmentaryline section of the member 3.) l

1n au forms of `the invention it will be seen thatrthe toggle effect isobtained for the upper supporting or bridgermembe'r, and that a very Thefuse can be readily re-iused and used over` and over again. In each formof the invention the rattachment of the fuse link'is of Very simpleAconstruction and is easy tof operate.

Further it is'to be particularly noted that the soldered joint in allforms of the invention is in pure shear and is not subjected to tensilestresses, which would cause an inaccuracy in the functioning of thefuse, as has been developed in great detail hereinabove.

The fuse link itself isrernarkably sturdy, although it may be smallcapacities. This permits the free han- V'dling of the fuse link inre-fusing'without danger of damage thereto.

It is to be distinctly understood that although a cork i l has beenshown only in the form illus- Ytrated in Figures 1 and 2 of thedrawings, that nevertheless it may be used with any other form of theinvention. Further, it is to be noted that the cork could be replaced bysome -other material or some other type of member which would o'ier agreater area'cf contact, either with the outrushing gases or with thepressure gases below its bottom face, so that it would assist in theaction of clearing the fuse, as will be hereinafter described, althoughit has been found from actual practicev that the cork is well suited tothis purpose'.Y The invention, however, is not limited to the use ofarcork alone, but other material or other members could replace thecork.

It is to be noted that the cork actually furnishes an additional areaof'contact with the outwardly rushing gases when the fuse blows and soassists in quickly removing the fuse, as it is bound thereto, Thisaction takes place not only from the pressure developed on the undersideof the cork by the outwardlyrushing jgases, but also'by the rictionalcontact of these outwardly rushing gases with the-side of the cork.Obviously another member could replace` Vthe cork and come within thespirit of this invention.

ln addition to these functions, the cork per- Vforms an additionalfunction. It mechanically binds the partsl of the fuseV strips togetherand assists in preventing breaking of the fuse, particularly duringhandling or re-fusing.- It prevents kinkingV of the fuse or breaking Vorthe fuse at the soldered joint, as it provides a mechanical reinforcingagency for this portion of the fuse strip, particularly as it extendscompletely over the soldered joint and over the ends of the solderedjoint. v ,Y Y Y Y It will be seen that a novel form of fuse has beenprovided by this invention in which the 12R watts developed at thesoldered joint is substan- Atially constant, irrespective of the ratingor ca pacity oir-the fuse, and that the calibration of fuses of diierentratings or the production by quantity production methods of fuses ofany. de-

built for small overloads or inv sired rating may be easilyfollowedlwith a resulting substantially constant accuracy.

Although 'this invention has been Vdescribed considerable detail, it isto be understood that such description vis intended vas illustrativerather than limiting,rv as the invention may be variously embodied andis to be interpreted as claimed.

Iclaim:V Y f l. A liquid fuse comprising a tubular'body portion,v anupper annular contact, an upwardly bowed member spanning said annularcontact and having its ends supported from saidr annular contact, aVfuse .link having an Lipper portion" formed of two strips independentlysecured'to said upwardly bowed member, said fuse link eX-tending'downwardly from the central portion of' said upwardly bowedmember, a lower contact electrically connected to said fuse, and a sprin1 for placing tension on said fuse link. v Y

2. A fusecoinprising an annular contact,a

fuse link, a toggle member supporting said fuselink and forcing an endof said fuse link into' engagementwith an inner wall of said contact,

a second contact electrically connected totheA kother end of saidfuselink, and a spring for placing tension on said fuse link.

3. Affuse comprising a Contact, a conducting fitting, a spring tendingto pull said fitting in a direction away from said contact, a fuse linkbetween said contact and fitting, and wedging means at each end of saidlfuse link for forcingv said fuse link into binding engagement withv saidcontact and said fitting, the wedging action ben ing produced by thepull of said spring, said fuse link being in direct contact with bothVvsaid contact and said fitting and said wedging means increasingthecontact pressure directly between said use link and said contact andsaid fitting.

4. A liquid fuse comprising a tubular body portionadapted to hold an arcextinguishing liquid, an annular upper contact anda lower contactcarried by said body portion, said annular contact having opposednotches, an upwardly` bowed member having its ends positioned withinsaid notches, a fuse link extending through the central portion of saidmember and having a pair of upper ends passing through said meniber, alower contact', a spring having its lower end secured. to said Vlowercontact, 9. tting sel cured to the upper end of said spring, said fuselink having a lower portion engaging said fitting, and a wedge forforcing said lower portion against said tting.

5. A liquid fuse comprising a tubular bodyportion adapted to hold an arcextinguishing liquid, a, lower and an upper contact carried by the bodyportion, said upper contact having opposed shouldered portions, an archshaped mem- .K

berhaving projecting arms seated on said op- Y posed shoulders Vandsupported byV said shoul` ders, a fuse link suspended from anintermediate portion of the arch shaped member and having one endpositioned between one of the arms lof,

said arch shaped member and one of said shoulders, and-a springoperatively coupled to the lower endYof-the fr-use link and to the lowercontact, said arch shaped member having a toggle action forcing theupper end of the fuse link into direct binding engagement with saidupper' contact..

RALPH H. EARLE.

